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https://hdl.handle.net/11681/3313| Title: | Sediment resuspension dynamics in canopy- and meadow-forming submersed macrophyte communities |
| Authors: | Aquatic Plant Control Research Program (U.S.) James, William F., Aquatic biologist Barko, John W. |
| Keywords: | Macrophytes Resuspension Sediment Shallow lakes Aquatic plants Aquatic vegetation |
| Publisher: | Environmental Laboratory (U.S.) Engineer Research and Development Center (U.S.) |
| Series/Report no.: | ERDC/EL SR ; 00-8. |
| Description: | Special Report Abstract: We examined the impacts of macrophyte beds dominated by a canopy-forming (Myriophyllum sibiricum) and a meadow-forming (Chara) species on shear stress near the sediment interface and resuspension in the large (1,620 ha) and shallow (1.25 m) Lake Cristina, Minnesota. The surface sediments in the vicinity of an adjacent M. sibiricum and Chara station, located in the northern region of the lake, exhibited a high moisture content (85 percent), low sediment density (0.2 g/mL), and high organic matter content (16 percent), indicative of fine-grained, flocculent sediment. The critical shear stress (tc) of these sediments, measured experimentally in the laboratory using a particle entrainment simulator, was low (1.4 dynes/cm²) and indicated a strong potential for resuspension at moderate wind speeds in the absence of submersed macrophytes. Between late July and September 1998, theoretical shear stress (t), calculated using wind data, and wave theory (i.e., assuming no macrophyte biomass in the lake to obstruct wave activity) exceeded the experimentally derived sediment critical shear stress 16 percent of the time. However, in situ turbidity at both the canopy-forming M. sibiricum and meadow-forming Chara station was low and rarely increased when t exceeded tc, indicating that both macrophyte beds reduced sediment resuspension in the lake. In situ shear stress, measured using calibrated gypsum spheres, was high near the open water lake surface during periods of high winds. However, it declined to near zero within the zone of Chara growth (30 to 40 cm) just above the sediment interface and was low both near the water surface and near the sediment interface in the canopy-forming M. sibiricum bed. Our results indicate that both canopy-forming and meadow-forming macrophyte communities can reduce sediment resuspension by dampening wave activity and shear stresses required to resuspend sediments. |
| Rights: | Approved for public release; distribution is unlimited. |
| URI: | http://hdl.handle.net/11681/3313 |
| Appears in Collections: | Special Report |
